U.S. patent number 5,327,116 [Application Number 07/999,597] was granted by the patent office on 1994-07-05 for low trailer tire detection device.
Invention is credited to Billy D. Davidson.
United States Patent |
5,327,116 |
Davidson |
July 5, 1994 |
Low trailer tire detection device
Abstract
A low tire pressure sensor for use in detecting deflation of a
tire while it is supporting a tow trailer from a surface as it
moves in a given direction therealong. The sensor comprises a
sealed housing holding a pivot shaft and enclosing an electrical
contact switch which is activatable upon rotation of the pivot
shaft from a first biased position to a second position. The pivot
shaft has an outside portion which extends sealingly and rotatably
through a portion of the housing. A resilient sensor rod is mounted
on the outside portion of the pivot shaft and extends therefrom at
an angle forward in the direction of movement of the tire when the
pivot shaft is in a first biased position. The resilient sensor rod
has an end spaced a predetermined distance from the surface, such
that upon at least partial deflation of the tire, the resilient
sensor rod contacts the surface and is moved over center to rotate
the pivot shaft to a second switch position, at which the
electrical contact switch is activated. A remote signal device is
connected through an electrical circuit to the switch so that it is
activated upon rotation of the pivot shaft from the first biased
position to the second switch activation position.
Inventors: |
Davidson; Billy D. (Dallas,
TX) |
Family
ID: |
25546512 |
Appl.
No.: |
07/999,597 |
Filed: |
December 31, 1992 |
Current U.S.
Class: |
340/443; 116/34R;
200/61.24 |
Current CPC
Class: |
B60C
23/08 (20130101) |
Current International
Class: |
B60C
23/08 (20060101); B60C 23/06 (20060101); B60C
023/00 (); B60C 023/06 () |
Field of
Search: |
;73/146.5,146.4,146.2
;340/443,442,437,436 ;116/34R ;200/61.41,61.42,61.44,61.24 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Chilcot, Jr.; Richard E.
Assistant Examiner: Felber; Joseph L.
Attorney, Agent or Firm: Montgomery; John W.
Claims
What is claimed is:
1. A low tire pressure detection device for use in detecting
deflation of a tire while it is supporting a tow trailer from a
surface for movement in a forward direction therealong, said device
comprising:
(a) a sealed housing enclosing an electrical contact switch
activatable upon rotation of a pivot shaft from a first biased
non-signal position to a second signal position, which pivot shaft
has an outside portion which sealingly and rotatably extends
through a portion of said housing;
(b) a flexible resilient sensor rod mounted on said outside portion
of said pivot shaft extending therefrom at an angle forward in the
forward direction of movement of said tire with said pivot shaft in
said first biased non-signal position, said resilient sensor rod
having an end spaced a predetermined distance from said surface,
such that upon at least partial deflation of said tire, said
resilient sensor rod contacts said surface and is moved over center
to rotate said pivot shaft to said second signal position; and
(c) a remote signal device electrically activated upon rotation of
said pivot shaft to said second signal position.
2. A low tire pressure detection device as in claim 1 wherein said
resilient sensor rod further comprises a coil spring.
3. A low tire pressure detection device as in claim 1 wherein said
resilient sensor rod is adjustably clamped to said pivot shaft.
4. A low tire pressure detection device as in claim 1 further
comprising a hanger arm mounted to an axle extending substantially
horizontally therefrom for holding said resilient sensor rod in a
non-operating position.
5. A low tire pressure sensor as in claim 4 wherein said switch
enclosed within said housing further comprises:
(a) a cam formed on said pivot shaft within said housing;
(b) a grounded movable contact positioned adjacent said cam for
movement thereof upon rotation of said pivot shaft; and
(c) another contact spaced apart from said movable contact and
engageable therewith to complete an electrical circuit upon
rotation of said pivot shaft so that said cam moves said movable
contact into engagement with said other contact.
6. A low tire pressure detection device for use in detecting
deflation of a tire while it is supporting a tow trailer from a
surface for movement in a given direction therealong, said device
comprising:
(a) a sealed housing enclosing an electrical contact switch
activatable upon rotation of a pivot shaft from a first biased
non-signal position to a second signal position, which pivot shaft
has an outside portion which sealingly and rotatably extends
through a portion of said housing wherein said switch enclosed
within said housing further comprises:
(i) a cam formed on said pivot shaft within said housing for
rotation with said pivot shaft;
(ii) a flexible contact positioned adjacent said cam for movement
of said flexible contact upon rotation of said pivot shaft from
said first biased non-signal position to said second signal
position; and
(iii) a fixed contact spaced apart from said flexible contact
engageable by said flexible contact to complete an electrical
circuit upon rotation of said pivot shaft from said first biased
non-signal position to said second signal position, such that said
cam moves said flexible contact;
(b) a resilient sensor rod mounted on said outside portion of said
pivot shaft extending therefrom at an angle forward in the
direction of movement of said tire with said pivot shaft in said
first biased non-signal position, said resilient sensor rod having
an end spaced a predetermined distance from said surface, such that
upon at least partial deflation of said tire, said resilient sensor
rod contacts said surface and is moved over center to rotate said
pivot shaft to said second signal position; and
(c) a remote signal device electrically activated upon rotation of
said pivot shaft to said second signal position.
7. A low tire pressure detection device for use in detecting
deflation of a tire while it is supporting a tow trailer from a
surface for movement in a given direction therealong, said device
comprising:
(a) a sealed housing enclosing an electrical contact switch
activatable upon rotation of a pivot shaft from a first biased
non-signal position to a second signal position, which pivot shaft
has an outside portion which sealingly and rotatably extends
through a portion of said housing, wherein said sealed housing
further includes an injection molded housing having a closed side
and an open side, a bearing formed in said housing and sized for
rotational support of said pivot shaft, a seal held in said closed
side of said housing coaxially with said bearing for sealing said
pivot shaft extending therethrough, and a cap sealingly engageable
in said open end of said housing to thereby seal said housing;
(b) a resilient sensor rod mounted on said outside portion of said
pivot shaft extending therefrom at an angle forward in the
direction of movement of said tire with said pivot shaft in said
first biased non-signal position, said resilient sensor rod having
an end spaced a predetermined distance from said surface, such that
upon at least partial deflation of said tire, said resilient sensor
rod contacts said surface and is moved over center to rotate said
pivot shaft to said second signal position; and
(c) a remote signal device electrically activated upon rotation of
said pivot shaft to said second signal position.
8. A low tire pressure sensor for use in detecting deflation of a
tire while it is supporting a vehicle or trailer from a ground
surface comprising:
(a) a water-resistant housing;
(b) means for attaching said water-resistant housing to an axle
adjacent to said tire to be sensed;
(c) a pivot shaft horizontally supported through a seal in said
water-resistant housing substantially perpendicular to the
direction of motion of said vehicle and having a portion extending
inside said housing, another portion extending outside of said
housing, said pivot shaft being rotatable between a first rotation
position and a second rotation position;
(d) a resilient sensor rod mounted on said pivot shaft extending
therefrom spaced at an end thereof within a predetermined close
distance from said ground surface and biased forward at a slight
angle from vertical when it is in said first rotation position such
that deflation of said tire activates said sensor rod to rotate
said pivot shaft to said second rotation position;
(e) a switch mounted inside said water-resistant housing adjacent
to said inside portion of said pivot shaft and engageable upon
rotation of said pivot shaft from said first to said second
rotation position; and
(f) a signal means electrically interconnected with said switch for
signalling an operator upon rotation of said pivot shaft from said
first to said second rotation position.
9. A low tire pressure sensor as in claim 8 wherein said resilient
sensor rod further comprises a coil spring.
10. A low tire pressure sensor as in claim 8 wherein said resilient
sensor rod is adjustably clamped to said pivot shaft so that said
predetermined distance from said sensor rod end to said ground is
adjustable.
11. A low tire pressure sensor as in claim 8 wherein said switch
enclosed within said housing further comprises:
(a) a cam formed on said pivot shaft within said housing;
(b) a grounded movable contact positioned adjacent said cam for
movement thereof upon rotation of said pivot shaft; and
(c) another contact spaced apart from said movable contact and
engageable therewith to complete an electrical circuit upon
rotation of said pivot shaft so that said cam moves said movable
contact into engagement with said other contact.
12. A low tire pressure sensor as in claim 8 wherein said
water-resistant housing further comprises:
(a) an injection molded housing having a closed side and an open
side;
(b) a bearing boss formed rigidly supported in said housing having
a cylindrical bearing surface formed therein for rotational support
of said pivot shaft;
(c) a seal held in said closed side of said housing coaxially with
said cylindrical bearing surface for sealing said pivot shaft
extending therethrough; and
(d) a cap sealingly engageable in said open end of said housing to
thereby seal said housing.
Description
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a device for detecting flat tires
on tow trailers, and in particular, to a water-resistant, corrosion
resistant, and damage resistant low tire detector which
conveniently fastens to the axle of a trailer.
BACKGROUND OF THE INVENTION
The operator of a vehicle can normally sense when one of the
pneumatic tires on the vehicle becomes deflated because of a
tilting of the vehicle itself. However it is not as easy to sense
the occurrence of tire deflation in a trailer which is being towed
along a roadway behind the vehicle being driven. This is
particularly true where the tow trailer is of a size and dimension
relative to the vehicle such that the tires of the tow trailer are
not easily observed. Sensing a low tire on a trailer is also
difficult if it is connected to the vehicle through a ball hitch
which does not translate tilting motion of the trailer caused by
tire deflation. Further, tow trailers are often pulled along a
roadway at night, such that viewing the trailer is difficult.
Further, constant attention to and observation of a trailer being
towed can be distracting and particularly annoying to a driver with
a utility trailer, a boat trailer, a recreational camper trailer,
or another similar tow trailer.
In the past, various tire deflation warning devices and low tire
indicators have been designed which attach to an axle adjacent a
tire. Typically, such devices have an elongated rod, which is
spaced slightly above the ground and is guided straight up and down
for vertical movement upon contacting the road surface due to
deflation of the tire. Vertical movement of the rod activates an
electrical contact switch which is connected to a warning signal.
Such devices, for example, are disclosed in U.S. Pat. No. 2,639,342
issued to Cope in 1953 and U.S. Pat. No. 5,032,822 issued to Sweet
in 1991. It has been found that vertical actuation of the rod is
not likely to occur without a bending action also, unless the
deflation occurs while the vehicle is stopped. If deflation occurs
while the vehicle is moving, the frictional forces at the point of
contact between the vertically actuatable rod and the roadway
surface will tend to bend the rod and thereby render the device
inoperable. Rolling elements at the ground contacting end of the
sensor rod, such as that disclosed in the Sweet '822 patent are
designed to reduce this problem. Rolling elements of any effective
size will cause the cost of the device to be substantially
increased. Small diameter rolling contact, with a roadway of normal
roughness, is not likely to avoid bending the actuation rod.
Another tire pressure indicator, as disclosed in U.S. Pat. No.
2,740,007, provides for a small amount of angular movement, as well
as vertical movement, of the actuation rod. It is the small amount
of angular movement which first causes an electrical contact,
thereby indicating a deflated tire condition. However, the range of
movement of such a device in the '007 patent is not sufficient to
insure against damage where deflation occurs rapidly, as it does,
for example, in a complete blowout situation.
Various other devices have been disclosed in which the sensor rod
is constructed of a hollow coil spring with a flexible cable
extending through the center of the coil spring. Examples of such
devices are shown in U.S. Pat. Nos. 3,096,410 issued to Anderson in
1963 and U.S. Pat. No. 3,265,822 issued to Moulton in 1966. Both of
these devices rigidly connect the upper end of a coil spring to the
housing of the detection device. The coil spring has a distal end
having a ball or a cap which will contact the roadway surface upon
tire deflation. Between the contacting ball or cap and the rigidly
connected upper end of the spring, a fixed length cable is
connected. Thus, upon contacting the surface the spring is bent
backward, thereby increasing its length due to the arc, so that
relative movement of the fixed length flexible cable through the
center of the coil spring activates a switch mechanism, thereby
signalling the deflated tire condition. These devices require a
relatively complex and expensive spring and internal cable
mechanism plus connecting linkage and a switch mechanism which is
relatively complicated, and subject to wear. Further, the entire
mechanism is adversely affected by corrosion. For example, dirt and
road grime can cause malfunction. Further, if used in wet weather
conditions, or on a boat trailer which is periodically submerged in
water, the apparatus may corrode and jam or the switch may fail or
otherwise adversely affect reliability.
Other flat tire signal devices have been disclosed in U.S. Pat. No.
2,640,119 issued to Bradford, Jr. in 1953 and another U.S. Pat. No.
3,502,829 issued to Reynolds in 1970, which devices activate
electrical switch contact upon rotation of a rigid sensor rod about
a pivot axis located in the signal device housing. Such devices
depend upon a straight tension spring acting through a lever arm to
hold the sensor rod in a vertically downward position. Rotation of
the vertical rod about the pivot axis works against the linear
tension spring to actuate an electrical switch for a warning
signal. Neither of these devices provide for a pivot shaft for
activating a simplified electrical switch, the moving parts of
which are completely sealed in a weather resistant and water-tight
housing. Further, there is no disclosure of any mechanism for
flexible compensation of a vertical component of force which may be
imparted into the rotation mechanism upon tire deflation.
SUMMARY OF THE INVENTION
Applicant's inventive low trailer tire detection device overcomes
the foregoing drawbacks of the prior low tire warning devices by
providing a low tire pressure sensor for use in detecting deflation
of the tire while the tire is supporting a tow trailer from a
roadway surface as it moves in a given direction along the roadway.
A water-resistant and corrosion resistant housing encloses a
simplified and reliable electrical contact switch. The switch is
activatable upon rotation of a pivot shaft from a first biased
position to a second position. The pivot shaft has a cam surface
sealed inside of the housing which is connected to an outside end
which sealingly and rotatably extends through a portion of the
completely sealed housing. A resilient sensor rod is mounted on the
outside portion of the pivot shaft for rotation therewith. When the
pivot shaft is in a first biased position, the switch is open and
the resilient sensor rod is at a slight angle forward in the
direction of trailer movement. The distal end of the resilient
sensor rod is spaced a short clearance distance from the roadway
surface. Upon at least partial deflation of the tire, by an amount
corresponding to the predetermined spaced clearance distance, the
resilient sensor contacts the surface and is resiliently bent
backward to rotate the pivot shaft to the second switch activation
position. Advantageously, the forward angle causes the sensor rod
to "pop" over center into a stable rearward position. Any
potentially destructive vertical component of force is accommodated
by the resilience of the sensor rod. Upon activation of the sealed
switch inside of the housing, a remote signal device is
electrically activated to indicate to the operator, such as the
driver of a towing vehicle, that there is deflation in the trailer
tire.
Thus, it is an object of the invention to provide a low tire
pressure sensor which is waterproof, sealed against water and
contaminant infiltration. The electrical contacts are totally
enclosed, as are all bearing surfaces within a sealed housing. The
housing is openable for maintenance; but, during operation, the
housing remains totally sealed from exposure to outside
conditions.
Further, it is an object of the invention to provide a low tire
pressure sensor which is activated by rotation and has a resilient
sensor rod to accommodate both potentially destructive bending
forces and vertical components of force. Preferably, the resilient
sensor rod extends at an angle forward of the rotatable pivot point
and moves over center upon tire deflation into a stable closed
switch condition. Both bending and compression forces are
accommodated through deflection of the resilient rod. The pivot
shaft rotates into a second switch activation position without
damage to the sensor device.
It is a further object of the invention to provide a
water-resistant and reliable low tire pressure sensor which can be
cost effectively manufactured with an injection molded housing,
reliable component construction, and simplified assembly.
Preferably, reliability is further enhanced through the use of a
torsional spring to continually bias a sensor rod into a
non-activated position until deflation of a tire occurs.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and advantages will be more fully
understood with reference to the following detailed description,
claims, and drawings, in which like numerals represent like
elements and in which:
FIG. 1 is a partial schematic side view of a low trailer tire
detection and warning device attached under a trailer frame to an
axle adjacent a rolling tire;
FIG. 2 is a partial cut-away cross-sectional view in the direction
of section line 2--2 of the low tire detection and warning device
shown in FIG. 1 according to the present invention;
FIG. 3 is a left end view of a sealed housing of the low tire
detection device of FIG. 2;
FIG. 4 is a right end view of a sealed housing of the low tire
detection device of FIG. 2;
FIG. 5 is a partial cross-sectional view of the sealable housing
taken along line 5--5 of FIG. 2 showing a non-activated switch
position; and
FIG. 6 is a partial cross-sectional view of the sealed housing of a
low tire detection device according to the present invention
showing an activated switch position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a partial schematic view of a low trailer tire
detection and warning device, generally designated as number 10,
which is mounted under a trailer or vehicle frame 12. The device is
clamped to an axle 14 which is typically supported with suspension
means 18 from the trailer frame 12 and which has tires 20 (one
shown) rotating coaxially with axis 16 of axle 14. The detection
device 10 comprises a device housing 22 which is clamped directly
to axle 14 adjacent to the inside of each tire 20 or on the inside
of each set of tires for larger trailers. For example, the housing
may have a base 24 around which a clamp 26, such as a hose clamp or
other strap clamp is fitted for securely attaching the housing to
the outside of any non-rotating axle, whether cylindrical shaped or
rectangular shaped. Where the housing 22 is mounted toward the rear
of the trailer axle relative to the direction of trailer motion 42,
the housing is shielded from debris by the axle 14. The device
housing 22 has a side wall 28 through which a rotation shaft 30
extends. Rotation shaft 30 has a resilient sensor rod 32 attached
to it so that movement of the sensor rod 32 causes rotation of
shaft 30. The attachment of rod 32 to shaft 30 can conveniently be
made through a bolt arrangement such as a U-bolt 34 fitted around
upper end 36 of resilient sensor rod 32. The sensor rod 32 extends
downward toward the ground such that a contact end 38 is spaced a
short distance 39 above a roadway surface 40. The spatial distance
39 is conveniently adjustable by loosening connector bolt 34, so
that it will slip about upper portion 36 of sensor rod 32, and then
by tightening it again when located properly. Preferably, the
sensor rod 32 is constructed of a resilient and durable material,
such as a metallic coil spring, which is corrosion resistant.
Preferably, a durable steel spring which may be coated with a
corrosion resistant coating, such as a galvanized electroplating,
or the like.
Preferably also, the sensor rod 32 is normally positioned for
operation at an angle 41, slightly forward of rotation shaft 30 in
the direction of trailer motion 42. However, a hanger arm 43 can be
advantageously attached as by clamping it to axle 14, so that the
resilient sensor rod 32 can be held by the hanger arm 43 in a
non-operating position 49. This allows the user to conveniently
prevent excess rubbing and needless wear in deep mud or deep snow
road conditions.
The end 38 of sensor rod 32 contacts the ground when the tire is at
least partially deflated. The slightly forward angle 41 of the
resilient sensor rod 32 advantageously allows it to move rearward
into a stable tilted backward position upon partial deflation while
the trailer is moving, as shown with phantom lines at 45. Also, if
deflation occurs while standing still, the resilient rod will bend
into an arc causing shaft 30 to rotate into a warning signal
position as shown with phantom lines 47. This reliably rotates
shaft 30 into its warning signal position when the trailer is
moving. Also, as the sensor rod 32 is made of a resilient material
and preferably is made of a metallic coil spring which has a small
amount of compressibility, as well as bendability, the motion of
the spring over center from the angled forward position while
moving or while standing, can be easily accommodated with the
spring action of the resilient sensor rod 32 absorbing any vertical
forced imparted to the sensor rod.
FIG. 2 shows a partial cut-away cross-sectional view of the
interior of the sensor housing in the direction of section line
2--2 through the housing 22. Housing 22 comprises a housing cup 44
having a closable interior cavity 46. Preferably, the housing cup
44 is substantially cylindrical having a central cup axis 48. A
closable opening 50, which is formed in the housing 22 on the side
opposite from side wall 28 and conveniently allows assembly,
further permits replacement or repair of internal parts in the
event that maintenance is ever required.
A symmetrical end cap 51 preferably comprises a cylindrical
insertion plug portion 94 sized for slip fit insertion into smooth
cylindrical sealing surface 84. A stop lip 96 abuts against the
exterior of opening 50 on housing 22. Insertion plug portion 94 has
a sealing ring 98 which is preferably an O-ring 98 positioned in an
O-ring groove 97. Threaded fasteners 100 are positioned through
attachment orifices 102 in lip portion 96 to engage threaded
fastening holes 86 so that the internal moving parts, including
shaft 30, torsion spring 56 and contact switch 64, are sealed
within housing 22 against moisture and dirt infiltration.
Preferably upon assembly, the interior of the housing is thoroughly
dried so that any corrosive activity over an extended time period
is substantially eliminated.
Rotation shaft 30 is rotatable about a shaft axis 52 which is
offset from cup housing axis 48 to permit the housing 22 to be of a
minimum size while accommodating the internal switching mechanism
64 as will be discussed more fully below. Shaft 30 is held for
smooth rotation in a shaft rotational bearing boss 54. Preferably,
shaft 30 has an external end 55 which extends through a shaft seal
56 mounted in housing side wall 28. Preferably, shaft seal 56 is a
resilient water-tight seal of the type which permits rotation, yet
seals against air and moisture infiltration. The housing 22 is
further advantageously molded with a smooth interior cylindrical
sealing surface 84 adjacent open end 50. Exterior cap fastening
means, such as threaded fasteners 100 in threaded holes 86, may be
formed around the opening 50 to permit secure and water-tight
closure of the housing.
FIG. 2 further depicts the internal washer 88 which is held in
position with pin 60 adjacent to bearing boss 54. The bearing boss
preferably has a smooth cylindrical bearing surface 92 formed
therein through which shaft 30 rotates and external to the
rotational shaft seal 56, an external locating washer 89 is
securely held in place as with a circular clip 87 or with a pin or
with other holding means 87 to prevent it from slipping off of
shaft 30.
FIG. 3 shows a close-up left side view of the sensor housing 22 of
FIG. 2 shown attached to axle 14 with clamp 26 around base 24.
Clamping flange 82 may also be integrally injection molded and in
fact, clamping flanges 82 may be conveniently formed as part of
base 24 on each side of the housing 22 to facilitate secure
clamping as with two hose clamps 26 on either side of the
housing.
FIG. 4 shows a close-up right side view of sensor housing 22 of
FIG. 2 shown with sealing end cap 51 removably attached with
fasteners 100.
FIGS. 5 and 6 are partial cut-away end views of an injection molded
water-tight housing 22, taken along section line 5--5. FIG. 5 shows
switch 64 in a first non-activated switch position. FIG. 6 shows
switch 64 in a second activated position. A torsional bias spring
58 holds shaft 30 in a first rotational position at which a shaft
stop pin 60 is held firmly against housing stop block 62. In this
position, the resilient sensor rod 32 is in the angled forward
position as previously described. Advantageously, switch 64 is a
simple and reliable contact switch which may be composed of a fixed
contact 66 and a flex contact 68. Flex contact 68 is positioned
adjacent a shaft cam 70 which is advantageously a flat surface
formed partially into the exterior of rotational shaft 30. Rotation
of shaft 30 causes shaft cam 70 to push against flex contact 68 and
move flex contact 68 into electrical contacting engagement with
fixed contact 66. Both fixed contact 66 and flexed contact 68 may
be conveniently economically constructed of a strip of stainless
steel material or other electrically conducting and non-corrosive
materials. The flexure can be advantageously provided by
constructing contacts 66 and 68 of a thin steel material which
resiliently returns to its non-contacting position when not
actuated through the rotation of shaft cam 70 on shaft 30. The
contacts 68 and 66 may be held in an insulating contact holding
boss 67 in the appropriate spaced apart non-contacting position
until the deflation of the tire causes sensor rod 32 to actuate
rotation of shaft 30. The insulated contact holding boss 67 may be
conveniently molded directly into the injection molded housing 22
or may alternatively be constructed of a resilient polymeric or
rubber material adhered to the inside of housing 22. Flexibility of
contacts 66 and 68 avoids breakage due to sudden impact of sensor
rod 32 or sudden rotation of rotation shaft 30.
Subsequently (as shown in FIG. 6), upon tire deflation, sensor rod
32 moves rearwardly and rotates shaft 30. Cam 70 engages flex
contact 66 and moves it against contact 68. Extending from fixed
contact 66 and flex contact 68 are electrical conductors 69 which
sealingly and insulatively extend through housing 22 and are
interconnected through electrical circuit means 71 to a warning
device 73 in the cab of the vehicle pulling the trailer.
Preferably, the wire connections extend to an existing trailer
connection plug 75 which interconnects with a vehicle connector
plug 77 so that the warning device 73 is activated in the towing
vehicle cab upon closure of the electrical circuit through contact
of flex contact with the fixed contact 66.
Housing 22 is advantageously made of injection molded plastic.
Shaft 30 is securely supported with a minimum of plastic material
through the use of appropriately positioned molded support struts
74, 76 and 78. One of the support struts, such as strut 78, can be
further molded with a boss 80 to which housing stop block 62 is
affixed in an appropriate position such that torsion bias spring 58
rotates shaft stop pin 60 into an abutting relationship against
stop block 62. This simplified construction reliably holds shaft 30
and attached resilient sensor rod 32 in the desired downwardly
projecting non-activated sensor position (as shown in FIG. 5).
Further, after activation and tire repair, the sensor rod
automatically moves back from the activated position (as shown in
FIG. 6) to the non-activated position.
Thus, what has been disclosed is a water-tight low pressure tire
warning device which may be constructed of a cost-effective two
piece injection molding with a single rotational shaft and an
inexpensive reliable electrical contact switch. The device is
conveniently attached to an axle and advantageously provides a
resilient sensor rod which contacts the ground upon deflation of
the tire. The resiliency of the sensor rod allows non-destructive
contact with a roadway surface to occur even at high speed and
rough roadway conditions. Further, the unique rotational axle
provides for complete and simple sealing so that the internal
mechanism is not adversely affected by contaminants such as water
or even salt water, thereby providing a trailer warning device
useful on boat trailers and the like. Further, the forward angle of
the sensor rod is uniquely and advantageously permitted through the
use of a resilient sensor rod and provides the additional benefit
of moving the sensor rod over center into a switch activated
condition, thereby reducing the occurrences of false indications of
tire deflation due to bouncing, as may result using a vertically
extending sensor rod.
While the invention has been described in connection with a
preferred embodiment, it is not intended to limit the scope of the
invention to the particular form set forth, but, on the contrary,
it is intended to cover such alternatives, modifications, and
equivalents as may be included within the spirit and scope of the
invention as defined in the appended claims.
* * * * *